A "drag and drop" operation refers to an operation in which a user selects a screen object by using a mouse to position a mouse indicator to point at a screen object, depresses a button on the mouse ("mouse button"), uses the mouse to move the selected screen object to a destination and releases the mouse button to drop the screen object on the destination. Typically, after releasing the mouse button, the screen object appears to have moved from where it was first located to the destination. The term "screen objects" refers generally to any object displayed on a video display. Such objects include representations of files, folders, documents, databases, and spreadsheets. In addition to screen objects, the drag and drop operation can be used on selected information such as text, database records, graphic data or spreadsheet cells.
During a drag and drop operation, the destination may, in some instances, not be visible. That is, a window controls access to various screen objects. Depending on the size of the window, the size of the screen objects and the number of the screen objects under its control, the window may only be able to display a subset of the screen objects. In this case, when the destination is a screen object that is not within the subset currently being displayed, scrolling the window to reveal the destination is necessary before the user can drop the screen object at the destination. The term "scrolling" refers to changing the subset of information displayed to a user. The subset of information displayed by a window can also be referred to as the "view" of the window.
Conventional systems provide a mechanism for automatically scrolling a window during a drag and drop operation. Such a conventional system is depicted in FIG. 1. FIG. 1 depicts a video display 102 that is displaying the components of a conventional system for automatically scrolling a window during a drag and drop operation. A mouse indicator 116, a screen object 114, and a window 104 appear on the video display 102. The mouse indicator 116 reflects the movement of a mouse input device. The window 104 contains a command region 124, a display area 122, and a scroll bar 106. The command region 124 displays various pull-down menus that contain commands that can be performed on screen objects 118, 120. The display area 122 displays contents of the window, like screen objects 118, 120 or other information.
Sometimes all of the contents of a window cannot fit within the display area 122. In this case, a scroll bar 106 is presented to the user so that the user can manipulate the subset of the contents presented to the user in the display area 122. The scroll bar 106 contains a left arrow movement control 110, a grey area 132, a scroll bar thumb 134 and a right arrow movement control 108. The left arrow movement control 110 shifts the view of the display area 122 to the left one unit each time it is activated. A "unit" is a uniform amount of information to scroll and is specific to the computer program that displays the window 104. For example, if the window 104 were displayed by a word processor, the unit may be one line of text when scrolling up or down, and one tab position when scrolling left or right. Activation of the grey area 132 shifts the view of the display area 122 one window-worth of contents at a time; that is, the amount of contents that can be displayed in the display area. If the activation occurs in the grey area 132 to the left of the scroll bar thumb 134, the view shifts to the left and if the activation occurs to the right of the scroll bar thumb, the view shifts to the right. The scroll bar thumb 134 provides a logical reference point relative to the information under the control of the window 104. For example, if the display area 122 is displaying information located near the end of the information under the control of the window, the scroll bar thumb 134 will appear close to the right arrow movement control 108. The right arrow movement control 108, when activated, shifts the view of the display area 122 to the right one unit. Activation of the previously mentioned controls occurs when a user initially selects the control (or grey area) by depressing the mouse button, as well as when the user keeps the mouse button depressed after selecting the control. While the mouse button is depressed, an activation occurs alter every lapse of a preset amount of time.
In utilizing the conventional system for performing automatic scrolling during a drag and drop operation, the user first selects a screen object 114 with the mouse indicator 116. The user performs this operation by positioning the mouse indicator 116 to refer to the screen object 114 and then depressing the mouse button. After depressing the mouse button, the user drags the screen object 114 across the scroll bar 106, thereby activating the scroll bar. Once the mouse indicator 116 is positioned over the scroll bar 106, the scroll bar 106 is invoked and the window automatically scrolls. If, for example, the mouse indicator is positioned over the left arrow movement control 110, the view of the display area 122 moves one unit to the left. If the mouse indicator 116 is positioned over the grey area 132, the view of the display area 122 moves one window-worth of contents. If the mouse indicator 116 is positioned over the right arrow movement control 108, the view of the display area 122 moves one unit to the right.
Thus, automatic scrolling occurs in conventional systems based solely on the location of the mouse indicator 116 during the drag and drop operation. Oftentimes, however, when a user is dragging a screen object, the user may be dragging the screen object over a number of windows before reaching the destination. Using conventional systems, when dragging over these windows, if the mouse indicator is positioned over a scroll bar, the display area of the window will scroll. This can have an undesirable effect of changing the view of the windows being utilized by a user and require that the user, after the drag and drop operation is performed, return the windows to their original views. Such unwanted scrolling can cause the user to perform their work less efficiently, as well as lead to user frustration.